While coal-fired power plants are notoriusly dirity, some are a lot worse than others. They are usually the older plants.
One that has long galled me is the old, but big, 4-corners power plant near the Four Corners area of Utah, New Mexico, Arizona, and Colorado. It spews its pall over the scenic canyonlands country and the Grand Canyon, and as the article indicates, is a prime example of environmental racism because it was imposed on an area with a lot of poor Native Americans (along with still other coal plants, strip mines, and leaky natural gas wells).
Story. 50 Dirtiest Power Plants. ENS